1. Field of the Invention
This invention relates to a device for remote transmitting a signal which varies in relation to a pressure to be measured.
Instruments of this type are widely known and used in many fields, for example for remote indicating the oil pressure in the lubricating circuit of motor vehicle engines.
2. Description of the Prior Art
In this specific field, to which the invention refers, -- though not being strictly limited thereto -- devices are generally used at present, which may conventionally be defined as of "rheostatic" type.
Generally, in these devices, the deformation produced in an elastic membrane by the fluid pressure to be measured, is transformed into a movement of the slider of a rheostat, connected to an electric control circuit, so as to determine a relationship between pressure values and the rheostat resistance. The resistance variation is used in the electric circuit to modulate an electric current which is indicated on a suitable instrument.
A "rheostatic" device of the type heretofore described is illustrated for example in the Italian Pat. No. 927.642 in the name of the same applicant, and it is therefore considered unnecessary to describe its operation in greater detail.
Although rheostatic devices work, on the whole, in a satisfactory way, they show however some inconveniences -- particularly with regard to their indication accuracy and life -- if they are subjected to very high vibrational stresses, as often occurs when they are mounted on motor vehicles.
This derives mainly from the fact that the movement of the central point of the pressure-sensitive elastic membrane has to be amplified by more or less complicated mechanical systems, before being applied to the rheostat slider, so as to obtain a sufficiently wide stroke of the actual slider.
If subjected to high vibrations, these mechanical amplifying systems may however give rise to inconveniences such as an increase in the operating clearance between the various members, miscalibration, wear of the moving parts or even breakage.